[ARC5] BC-348-Q Capacitor Questions

[J. Forster]

>
> On Aug 23, 2010, at 2:08 AM, Henry Mei'l's wrote:
>
>> Hello Dennis
>>
>> How does this work?I don't have an HP 428 but is there some way I
>> can rig up
>> something using standard VTVMs/VOMs &/or scopes to do the same thing?
>>
>> ----- Original Message -----
>> From: "Dennis Monticelli" <dennis.monticelli at gmail.com>...
>>> I find that it is easier and less invasive to use an old HP 428
>>> clip-on
>>> current meter to check caps.
>
> Basically, here is how the HP clip-on milliammeter works:
>
> The clip on probe contains a magnetic core that is placed over the
> wire being tested.  The core is operated at a certain level of
> magnetic flux by the instrument.  The DC current in the wire under
> test, changes the flux in the core.  This change is detected by the
> instrument and there is a corresponding reduction of the flux in the
> core to return it to the original balanced state.

It's called a flux-gate sensor.

> So, the important parts of the system are:
>
> A unique clip-on core
> A source of magnetism in the core that is monitored by the instrument
> A feedback system to reduce the magnetism to restore the original flux
> level
> A metering system to display the detected current.
>
> Note: if you buy one of these HP meters without the clip-on probe, you
> have a useless piece of equipment.
>
> There are clip-on probes meant for use with oscilloscopes that detect
> AC currents in a wire, and may well be some that detect DC currents.
> Tektronix, naturally, had/has such AC detecting probes. The one I know
> of is quite old now, and had a little power supply and amplifier as
> part of the setup.  It's frequency response was modest, but I think it
> worked at line current and up to perhaps some couple of hundred kc.

Tek had the 6021 & 6022 that worked with either a passive termination or
the 134 amp, which went to a lower frequency, but not to DC.

Tek also made some DC current probes, like the 6032. The current unit uses
a similar technology with a TM500 amplifier module. These units go from DC
to 50+ MHz.

> I have a couple of devices that are called "Hall Effect sensors".
> These things are based on relatively new creations of modern physics
> that I don't understand, but I think they detect current in a wire
> that is passing through the opening in the thing.  Search via Google
> for "hall effect sensors" and you'll get lots to read. Apparently, you
> can buy them at Digi-Key.  This seems to be a promising avenue to
> explore.

They are a small, gapped core with a Hall Sensor in the gap.


est,

-John

=============
>
>
> Roy
>
> Roy Morgan
> k1lky at earthlink.net
> K1LKY Since 1958 - Keep 'em Glowing!
>
>
>
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>